The present invention relates to apparatus for separating heterogeneous mixtures of at least two liquid phases and, more particularly, to separation apparatus using “reverse flow” settling.
Solvent extraction is used generally in industry to recover a targeted dissolved product. For example, it is common to process metal ore using multiple steps, some of which may involve moving the targeted product from an organic solvent to an aqueous solvent, or conversely, from the aqueous solvent to the organic solvent. To effect the movement of the targeted product between the various phases, the phases are mixed to enhance surface area contact between the phases, and the heterogeneous mixture of a dispersed phase in a continuous phase is then introduced into a rectangular or cylindrical separation tank, wherein separated effluents are removed after the mixture has been subjected to a flow regime that is as non-turbulent as possible. The flow velocity should be sufficiently low, and the flow path sufficiently long, to enable separation between the phases and settling. The flow must also be directed in such a way to prevent recirculation and turbulence, in order to prevent separated components of the mixture from mixing once again.
U.S. Pat. No. 5,266,191 to Greene et al. teaches non-turbulent flow separation using closely spaced longitudinally mounted plates and a serpentine flow path. U.S. Pat. No. 5,558,780 to Vancas, assigned to Bateman Engineering Inc., teaches a reverse flow settler apparatus, with several advancements, notably influent entry into a coalescence chamber along an outside side wall of the separator tank, turning of the mixture at one end of the separator, passing the mixture through picket fences, installed across the settler width, for turbulence and flow distribution control and then into the settler basin proper. In this arrangement, some pre-separation may occur before entry of the mixture into the settler basin. The separated effluents are removed at the other end of the separator, which is the same end of the apparatus as the end receiving the influent feed. Moreover, most of the mixing equipment and the associated agitator maintenance operations may be located contiguously on one side of the separator installation.
These advancements notwithstanding, the present inventors have recognized the need for an improved reverse flow settler apparatus.